Dust Eyed as Cause of Nuke Alarms

Thursday, May 3, 2012 @ 06:05 PM gHale

Airborne dust looks like it might be the culprit behind an unusual event declaration following an accidental shutdown Monday morning at the Salem Unit 1 nuclear reactor along the Delaware River in New Jersey.

Safety systems at one point indicated a fire inside the reactor’s containment structure, resulting in a lockout that delayed workers from entering the area and ruling out any blaze, said a Nuclear Regulatory Commission (NRC) report.

Although the reactor’s safety control rods successfully curbed the heat-generating reaction inside the plant core, the NRC report said, “PSEG believes the trip/safety injection may have caused pipe shaking that resulted in dust being stirred up near fire-detection equipment and led to the false fire alarms.”

PSEG Nuclear, which runs the plant, reported its employees were testing a turbine steam inlet Monday when emergency shutdown and cooling water injection signals accidentally triggered, setting off valve openings and closings and dust-raising vibrations as cooling systems and flows redirected.

The NRC is reviewing the incident to determine if it warrants classification as a more-serious type of operating mishap, said Neil Sheehan, an NRC regional office spokesman.

Federal rules allow plants to have up to an average of 3 unplanned control rod insertions in any 7,000-hour period before coming under stepped up scrutiny. More than one such incident in any 7,000-hour period can bring increased oversight, however, if there are complications.

Unusual events are the lowest category of emergency action levels used by the NRC, requiring notification of states and other federal agencies, without activation of the utility’s emergency operations.